The present invention relates to a method of forming tailored blanks to be used to produce shaped metal components.
Sheet metal components of complex shapes are typically produced from a planar blank that is formed into the finished shape through a series of forming or stamping operations. Where relatively complex components are to be produced, it is usual to build the component out of a number of individual elements, each of which is stamped from a blank. The need to use multiple components may result from the complexity of the finished product or may result from the different characteristics of the material required in different areas of the component. For example, if the component is a door frame of an automobile, the majority of the door frame may be formed from a relatively thin metal sheet but the mounting points for the hinges of the door require extra strength. The use of multiple elements to produce the finished component increases the manufacturing complexity.
To mitigate this complexity, it has been proposed to produce a tailored blank in which appropriately shaped sheets of material are connected edge to edge by a laser welding process to produce a unitary blank. When formed, the blank produces a component with differing material characteristics through the structure. This process permits optimum use of the material but at the same time minimizes the subsequent assembly of multiple elements into the final component.
The production of a tailored blank requires the constituent sheet metal parts to be cut accurately so that the laser welding may be performed efficiently and retain an adequate weld quality. This requires precision cutting of the constituent components and in our published Application Nos. 9624039.5 filed Nov. 19, 1996, 9624652.5 filed Nov. 27, 1996 and Application No. 9700251.3 filed Jan. 8, 1997, each of which were filed in Great Britain and are abandoned, various methods are described to mitigate the difficulties encountered with obtaining the required precision from the constituent parts. However, in certain circumstances, it is desirable to produce a formed component with a very high quality surface finish so that subsequent processing such as painting can be accomplished with a minimum of refurbishment of the surface after welding. While laser welding offers in general a relatively high-quality welded surface and the processes contemplated in the above-mentioned applications further facilitate the production of a smooth outer surface, there is nevertheless the need for a tailored blank that may be used directly to produce a finished surface.
It is therefore an object of the present invention to obviate or mitigate the above disadvantages.
In general terms, the present invention provides a tailored blank having a pair of sheet metal constituent parts each having a pair of oppositely directed major surfaces. A major surface of one of the components is placed on the major surface of another of the components and the parts welded to one another to produce a unitary blank. The blank may then be subsequently formed into a component of varying material characteristics.
Preferably the welding of the constituent parts is performed by laser welding and as a further preference, the laser welding does not penetrate to the other major surface of the other constituent part.